While I understand that you want to use a vintage gas valve for its looks, It's always much better and safer to use a brand new valve.
The local Gas Company in my city discourages customers from using old, worn out gas valve. Inspectors do too.

Ha ha ha....this time it is not for its looks, but its function. I just bought a brand new valve for $30. It will have to be modified in order to work and it is going to work backwards, which is going to bother me to no end. The ONLY reason I am not using the one in the photo above is because I accidentally broke it, so I can't use it.

Sophie, one of the most valuable assets a DIY'er in an old house can have is a relationship with locals in the various trades. Check around with the folks in the old-house HVAC business locally and I'll bet one of then will have what you need on hand. Get that one's business card since you might need them again, and put them on your Christmas card mailing list. Rumor has it that doing that can sometimes net you discount prices, but at worst they will remember you and be glad to help you again in the future!